| Spectroscopic investigations were performed to probe the structure of heavy elements, via K isomer studies in the region of heavy actinides. K isomers in 246Cm and 248Cm (Z = 96) were populated via deep-inelastic and transfer reactions. This reaction mechanism has been employed for the first time in trans-plutonium nuclei to study high-K isomers. The experiment was performed at Argonne National Laboratory using a pulsed 209Bi beam from the ATLAS superconducting linear accelerator, at an energy of 1450 keV (15 percent above the Coulomb barrier) incident on a long-lived 248Cm target. Data were collected in between beam pulses using Gammasphere, a 110-detector high-resolution germanium detector array, in various time regimes ranging from 1 microsecond up to 8 seconds, to adjust for different isomer half-lives. The half-life of a Kpi = 8- isomer in 246Cm, previously identified in the beta-decay of 246Am, has been measured for the first time to be 1.12(24) s. The Kpi = 8- isomer in 246 Cm has the same underlying 2-quasineutron [624]7/2 x [734]9/2 configuration, as is observed in the N = 150 isotones 250Fm and 252 No. A new high-K isomer has also been discovered in the N = 152 nucleus 248Cm, and its half-life measured to be 146(18) mus. These new data on high-K isomers add to the scant knowledge of single-particle and pair-gap energies in heavy actinides. The location of the neutron deformed sub-shell gap is confirmed to be at N = 152, from the experimental high-K energies of the isomeric states. The results of this experiment provide constraints on various theoretical models that predict the next magic shell gaps in the region of superheavy elements. |
